package com.lagou.slqSession;

import com.lagou.pojo.BoundSql;
import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;
import com.lagou.utils.GenericTokenParser;
import com.lagou.utils.ParameterMapping;
import com.lagou.utils.ParameterMappingTokenHandler;

import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class SimpleExecutor implements Executor {

    private PreparedStatement doPrepare(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {
        // 获取数据库连接
        Connection connection = configuration.getDataSource().getConnection();
        String sql = mappedStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);

        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());

        String parameterType = mappedStatement.getParameterType();
        Class<?> parameterTypeClass = getClassType(parameterType);

        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();

            Field declaredField = parameterTypeClass.getDeclaredField(content);
            declaredField.setAccessible(true);
            Object o = declaredField.get(params[0]);
            preparedStatement.setObject(i + 1, o);
        }
        return preparedStatement;
    }

    @Override
    public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {

        PreparedStatement preparedStatement = doPrepare(configuration, mappedStatement, params);

        ResultSet resultSet = preparedStatement.executeQuery();
        String resultType = mappedStatement.getResultType();
        Class<?> resultTypeClass = getClassType(resultType);

        List<Object> result = new ArrayList<>();
        while (resultSet.next()) {
            Object instance = resultTypeClass.newInstance();
            ResultSetMetaData metaData = resultSet.getMetaData();
            for (int i = 1; i <= metaData.getColumnCount(); i++) {
                String columnName = metaData.getColumnName(i);
                Object columnValue = resultSet.getObject(columnName);
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(instance, columnValue);
            }
            result.add(instance);
        }
        return (List<E>) result;
    }

    @Override
    public int update(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {
        PreparedStatement preparedStatement = doPrepare(configuration, mappedStatement, params);

        preparedStatement.executeUpdate();
        return preparedStatement.getUpdateCount();
    }

    private Class<?> getClassType(String parameterType) throws ClassNotFoundException {
        if (parameterType != null) {
            Class<?> clazz = Class.forName(parameterType);
            return clazz;
        }
        return null;
    }

    private BoundSql getBoundSql(String sql) {
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "}", parameterMappingTokenHandler);

        String parsedSql = genericTokenParser.parse(sql);
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();
        BoundSql boundSql = new BoundSql(parsedSql, parameterMappings);
        return boundSql;
    }
}
